Tag Archives: cooking and science

In sous vide cooking, food is cooked in a water-bath at low temperatures (130-150 F) for longer times. Food cooked sous vide can be radically different in texture and taste than food cooked by more traditional methods. Even better, sous vide cooking is really, really easy.

What is sous vide?

In sous vide cooking, food in plastic bags is placed in a fixed-temperature water bath. The water bath temperature is held most easily by a digital controller. Some people build their own systems on the cheap. I bought this one, which in my opinion is worth every bit of $200.

As I discussed last week, bacteria die above 125 F. Consequently, food can be cooked at any temperature above 125 F (the closer to 125 F, the longer required for sanitation). This means a steak can be cooked to 130 F and be rare throughout, but also safe. For a 1 inch thick steak, this takes about an hour.

Why is it different?

Like a crock pot, sous vide cooking can be used to make tough cuts of meat extremely tender. Unlike a crock pot, the user has precise control over the set temperature, and the food is isolated from the water in which it cooks. This means that sous vide food isn’t soggy like slow cooker food so often is.

When we cook meat, the textural and color changes we observe are due to changes in the protein of the meat. Different proteins break down at different temperatures. The controller I use (linked above) allows control down to 0.1 C or 0.5 F. With such fine control, the cook can choose the exact temperature at which they wish to cook, and thus the effect they’d like to have on the protein. Poached eggs best demonstrate the results of this control. The proteins in the yolk coagulate at lower temperatures than the proteins in the white. By changing the cooking temperature only slightly, the cook can dramatically change the textures in the poached egg. This is called the perfect egg–at the link you can see eggs cooked to a variety of temperatures.

The set-up

For my set-up, the only major cost was the controller. I clamp it to the edge of a 8 qt pot (bigger would be better, but it’s what I had). Many people vacuum-seal their food before cooking, but the sealing system is an additional cost. I put my food in ziplock bags (glad bags are reported to be BPA-free). Then I add a little oil, squeeze the air out, and seal. To start cooking, I wait for the water in the pot to heat up and I clip the bag to the edge of the pot with a clothes pin.

Recipes and further reading

Citizen sous vide: an excellent general guide, with links to recipes and product reviews. Recipes are sorted by meat and cut.

Recipe for tri-tip steak: this recipe suggests cooking a tri-tip at 130 F for 6 hours, results shown below. You can see the meat is still pink in the middle. Cooking for six hours allowed it to tenderize, and all I had to do was cut up some meat and stick it in a bag. Very easy and delicious.

The milk we get at the store is pasteurized, and we all know that chicken must reach 165 F and pork must reach 145 F. What is the source of these numbers, and what is their purpose?

Raw foods like meat and dairy contain a certain number of pathogens that can make us sick. These pathogens die when heated above about 125 F. So why are cooking temperatures much higher than 125 F? The recommended cooking temperatures are the temperatures your food must reach in order for a large enough portion of the bacteria to die nearly instantaneously. At 140 F, the salmonella in ground beef is reduced by a factor of ten every 5.48 minutes. Salmonella must be reduced by a factor of ten million to one, so you would have to hold this temperature for a while. At 150 F, the salmonella is reduced by a factor of ten every 0.55 minutes, so this is quite a bit faster. At 160 F, the bacteria reduces fast enough that by the time you’ve measured it, enough time has passed. The process of “sous vide” cooking uses lower temperatures applied steadily for long times to cook food. I will discuss this excellent cooking method in a future post.

The process of making food safe by reducing the bacteria is called pasteurization, which you may be more familiar with from the dairy aisle than meat, but the concept is the same. Also in dairy, the time for pasteurization depends upon the temperature. Pasteurized milk is heated to 162 F for at least 15 seconds while ultra-pasteurized milk is heated to 280 F for 1-2 seconds. Eggs are not usually pasteurized, but they can be when heated to 130 F for about an hour.

Douglas Baldwin’s section on food safety in his online guide to sous vide is the source of much of the information I present here. It is full of scientific citations, but is very readable, and I highly recommend it as further reading. Happy Valentine’s Day!

I love to cook. As one might gather from this blog, I like to keep my hands busy, and cooking saves money and provides deliciousness. (Many other hobbies have more of a knack for consuming money.) I also happen to be very lactose-intolerant, so cooking for myself also greatly benefits my digestive health.

When I was younger, I was absolutely apathetic to cooking, as I suspect many kids are, feeling that it’s house-wifely and unimportant. Then I got out on my own, and, astonishingly, good food was expensive and I had little currency. I wanted to improve my cooking, but I really didn’t know the rules. But I knew the next best thing: science. Many recently published books explore the relationship between science and cooking. For those of us that can’t remember the baking soda without knowing its chemical purpose, this is a great thing.

Some recommended books:

What Einstein Told his Cook by Robert Wolke. The content is good, especially for those less versed in chemistry. The author wrote a newspaper column about cooking, and this book is mostly the compilation of answers to various questions such as “What is the difference between cane sugar and beet sugar?” It contains several recipes illustrating various points of the book. A major emphasis of the book is clarifying common misunderstandings of food science. As someone who knows a lot of science, I sometimes find the answers too basic, but I definitely learned things reading this book.

Molecular Gastronomy: Exploring the Science of Flavor by Herve This. Of the three books I discuss, this is the one I have had the least time to scrutinize. However, I really like what I have read. Wolke’s book covers more conceptual topics, like the differences between various kinds of salts. This’s book covers more specific topics, like why we marinade roasts in red wine rather than white, or how different kinds of truffles are related. This one is probably most strictly for those interested in cooking, with fewer “gee whiz” moments and more “that would be useful” moments.

Cooking for Geeks: Real science, great hacks, and good food by Jeff Potter. This one is definitely the most fun of the three! This book is from the publisher O’Reilly, which does a lot of technical textbooks. This book shares its layout with those kinds of book, but its soul is lighter. Its layout is more varied, as textbooks are. Plus, this book has a fun section about hardware like evaporators and sous vide water baths. Sous vide is involves cooking foods in circulating water baths. It is similar to slow-cooking, but the food is kept in a plastic bag and thus not diluted. Foods can safely and extra-deliciously be cooked at much lower temperatures by this method. Low temperatures denature specific proteins, prevent drying, and, when held for a bit, kill bacteria. This book does a great job explaining why and how sous vide works. I just got a sous vide system myself, and this book has given me some confidence about something I knew very little about. Plus it’s very fun to read, and covers tons of other topics in geek-friendly ways.

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About Vironevaeh

I am a research scientist and artist living in New Mexico. This blog is a catch-all for my interest in science, art, and science fiction. If you're passionate about these topics, too, drop me a line on a post. I also post about New Mexico, the southwest, photography, and current projects.